Yeah I have thought about camping and vaping a few times since I started. I usually go for two weeks every summer so it should be interesting to see if I can keep up with charging.
We usually bring a little Honda EU2000i that we run for about 3 or 4 hours every couple of days to charge up our two-way radios, flashlights, etc. It runs pretty quiet and a tank of gas will last us the whole trip.
As an alternative some kind of solar panel + gel cell battery solution would be nice. That way you can keep a big battery constantly charging (with a charge controller/regulator of course) so you can recharge your PV batteries anytime day or night.
Charging eGo's should adapt easily to this sort of setup as they all charge by way of 5V DC.
For the bigger PV's that use IMR's, I do see that some trustfire chargers have dual AC and 12V DC barrel type inputs. With the rite adapters you should be able to charge your IMR's with solar without having to invert to AC.